NGC 404は非常に孤立した矮小レンズ状銀河であり、小マゼラン雲と比べ、少し明るくて小さい[8]。他の多くの早期型銀河と異なり、21cm線(中性水素原子)が非常に多く、その多くは周囲にある1対の大きな環に集中している[9]。また、その中心部[10]と最外縁の領域で、星形成が行われているが、それほど活発ではない[11]。
^ abJensen, Joseph B.; Tonry, John L.; Barris, Brian J.; Thompson, Rodger I. et al. (February 2003). “Measuring Distances and Probing the Unresolved Stellar Populations of Galaxies Using Infrared Surface Brightness Fluctuations”. Astrophysical Journal583 (2): 712–726. arXiv:astro-ph/0210129. Bibcode: 2003ApJ...583..712J. doi:10.1086/345430.
^ abI. D. Karachentsev; V. E. Karachentseva; W. K. Hutchmeier; D. I. Makarov (2004). “A Catalog of Neighboring Galaxies”. Astronomical Journal127 (4): 2031–2068. Bibcode: 2004AJ....127.2031K. doi:10.1086/382905.
^Karachentsev, I. D.; Kashibadze, O. G. (2006). “Masses of the local group and of the M81 group estimated from distortions in the local velocity field”. Astrophysics49 (1): 3–18. Bibcode: 2006Ap.....49....3K. doi:10.1007/s10511-006-0002-6.
^Materne, J. (April 1979). “The structure of nearby groups of galaxies - Quantitative membership probabilities”. Astronomy and Astrophysics74 (2): 235–243. Bibcode: 1979A&A....74..235M.
^ abMirach's Ghost (NGC 404), The Internet Encyclopedia of Science, David Darling. Accessed on line August 15, 2008.
^Karachentsev, Igor D.; Karachentseva, Valentina E.; Huchtmeier, Walter K.; Makarov, Dmitry I. (2003). “A Catalog of Neighboring Galaxies”. The Astronomical Journal127 (4): 2031–2068. Bibcode: 2004AJ....127.2031K. doi:10.1086/382905.
^del Río, M. S.; Brinks, E.; Cepa, J. (2004). “High-Resolution H I Observations of the Galaxy NGC 404: A Dwarf S0 with Abundant Interstellar Gas”. The Astronomical Journal128 (1): 89–102. arXiv:astro-ph/0403467. Bibcode: 2004AJ....128...89D. doi:10.1086/421358.
^ abThilker, David A.; Bianchi, Luciana; Schiminovich, David; Gil de Paz, Armando et al. (2010). “NGC 404: A Rejuvenated Lenticular Galaxy on a Merger-induced, Blueward Excursion Into the Green Valley”. The Astrophysical Journal Letters714 (1): L171–L175. arXiv:1003.4985. Bibcode: 2010ApJ...714L.171T. doi:10.1088/2041-8205/714/1/L171.
^Seth, Anil C.; Cappellari, Michele; Neumayer, Nadine; Caldwell, Nelson et al. (2010). “The NGC 404 Nucleus: Star Cluster and Possible Intermediate-mass Black Hole”. The Astrophysical Journal714 (1): 713–731. arXiv:1003.0680. Bibcode: 2010ApJ...714..713S. doi:10.1088/0004-637X/714/1/713.
^ abcRomanowsky, Aaron J.; Forbes, Duncan A.; Haynes, Martha P.; Donatiello, Giuseppe; Beasley, Michael A.; Makarov, Dmitry; Carballo-Bello, Julio A.; Longeard, Nicolas et al. (2018-12-01). “Mirach's Goblin: Discovery of a dwarf spheroidal galaxy behind the Andromeda galaxy” (英語). Astronomy & Astrophysics620: A126. arXiv:1810.04741. Bibcode: 2018A&A...620A.126M. doi:10.1051/0004-6361/201833302. ISSN1432-0746.